The present invention relates to ore or similar materials, and more particularly relates to methods for recovering at least one metallic element from ore or other material.
Processes for the recovery of cesium (Cs) from pollucite and other cesium-containing minerals were reviewed by J. J. Kennedy in Chemical Reviews, Vol. 23 (1938), pages 157-163. More recent technical developments were summarized by R. A. Heindl, Bureau of Mines Bulletin 650, “Mineral Facts and Problems” (1970 ed.), pages 527-534. In one process that has undergone considerable development for commercial use, ground pollucite ore is leached with strong sulfuric acid to obtain an extract containing cesium alum, which is recovered by crystallization for further processing. The cesium alum process has been considered a traditional process for recovering cesium from pollucite. However, other recovery processes have been proposed, as described in the above citations. The first step in most such processes is an acid leaching of the pollucite to obtain cesium as a soluble salt in a mixture with other metal salts. Such an acid extraction occurs readily with a variety of strong acids, including not only sulfuric acid, but also hydrobromic and hydrochloric acids.
As already mentioned, when sulfuric acid is used for the digestion step, the cesium can be recovered as cesium alum, expressed as CsAl(SO4)212H2O or Cs2 SO4Al2 (SO4)324H2O. Processes for further purification of cesium starting with a cesium alum are described in U.S. Pat. Nos. 4,469,670 and 4,466,950. When hydrobromic acid is used, the aluminum bromide can be removed first by isopropyl alcohol extraction, and thereafter the mixed alkali metal bromides are recovered and treated in an extractor to obtain a solution of cesium tribromide which, upon evaporation, yields cesium bromide.
Where hydrochloric acid is the extractant, the cesium can be precipitated by the addition of antimony chloride to form a precipitated antimony chloride (CsSbCl6), which can be separated and decomposed in water to form cesium chloride and a water-soluble compound of antimony. The cesium chloride can then be reacted with perchloric acid to produce crystals of cesium perchlorate, which can be recovered and then decomposed to obtain cesium chloride as the final product. (See U.S. Pat. No. 2,808,313.)
While the above described processes are capable of producing cesium sulfate, cesium bromide, and cesium chloride, the above processes are not capable of producing near 100% extraction yields of a low-assay ore. Additionally, these processes have proven to be difficult and expensive for commercial application. Therefore, there has been a recognized need for an improved process for recovering cesium from pollucite in a highly purified form. The need for such a process improvement has been emphasized in recent years by the increasing uses of cesium and cesium compounds, and by the projected expansion of these uses in anticipated applications. (See Heindl, above cited, pages 528-532.)
All of the patents and publications mentioned above and throughout are incorporated in their entirety by reference herein.